The conventional lock is disclosed in FIGS. 1 and 2, and generally includes a lock case 10 with a hole 101 defined therethrough. The case 10 has a space and a cam 20 is engaged with the space. Two cores 30 are connected to two ends of the cam 20 respectively and located in the case 10. A gap 102 is defined between the case 10 and the cam 20 and a positioning plate 103 is located in the gap 102 so as to position the cam 20 and the cores 30. The lock is connected to an object via the hole 101.
However, the unauthorized persons usually pick the top beads and the bottom beads in the cores 30 and to rotate the cam 20 to unlock the lock. If the arrangement of the top beads and the bottom beads is too complicated, the unauthorized persons break the case 10 at the position where the hole 101 is located as shown in FIG. 3 and the cores 30 are taken out or exposed, the cam 20 is then rotated to unlock the lock. This is to say, the lock can be unlocked if the case 10 is broken and the cores 30 are taken out. Furthermore, because each lock has a specific key which is shaped to match with the movement of the top and bottom beads, so that when the cores 30 are to be replaced, the whole case 10 has to be replaced too. This makes the maintenance cost high and the manufacturers have to prepare sufficient parts for maintenance.
The regulations for locks require the locks to have certain unlock times, levels of durability, fire-proof, the number of parts, material and specification. However, for combination locks, the small sized locks are difficult to obtain the required sets of combination numbers which need at least five sets of top and bottom beads. As shown in FIG. 2, when assembling the cores 30 and the cam 20 to the case 10, the positioning plate 103 is used in the gap 102 to position the cam 20 and the cores 30. The gap 102 restricts the length of the lock so that only four sets of top and bottom beads can be installed. The less number of the top and bottom beads cannot meet the requirements and the locks are easily unlocked.
The present invention intends to provide an anti-break lock which prevents the core from being unlocked even if the core is taken out.